A ring binder mechanism retains loose-leaf pages, such as hole-punched pages, in a file or notebook. It has ring members for retaining the pages. The ring members may be selectively opened to add or remove pages or closed to retain pages while allowing the pages to be moved along the ring members. The ring members mount on two adjacent hinge plates that join together about a pivot axis.
A housing loosely supports the hinge plates within the housing and holds the hinge plates together so they may pivot relative to the housing. The housing has a generally arch-shaped cross-section, with bent-under rims that hold the hinge plates within the housing. The hinge plates are disposed within and extend across the open bottom part of the arch spaced from the top of the arch and the ring members extend through notches or openings in the housing or in some cases around the sides of the housing.
The undeformed housing is narrower than the joined hinge plates when the hinge plates are in a coplanar position (180°). So as the hinge plates pivot through this coplanar position, they deform the resilient housing laterally outwardly and cause a spring force in the housing that urges the hinge plates to pivot away from the coplanar position, either opening or closing the ring members. Thus, when the ring members are closed the spring force resists hinge plate movement and clamps the ring members together. Similarly, when the ring members are open, the spring force holds them apart. An operator can overcome this force by manually pulling the ring members apart or pushing them together. Levers may also be provided on one or both ends of the housing for moving the ring members between the open and closed positions.
Some ring mechanisms include locking structure(s) that block the hinge plates from pivoting when the ring members are closed. The locking structure positively locks the closed ring members together, preventing them unintentionally opening if the ring mechanism is accidentally dropped. For example, locking structures can be incorporated on a control slide or travel bar moveable relative to the housing between a locking position in which locking elements block pivoting movement of the hinge plates and non-locking position in which the locking elements do not block movement of the hinge plates. The presence of a locking feature may facilitate use of a housing that provides a weaker spring force tending to hold the rings in the closed position. This can be desirable because it can be painful if a user accidentally gets his or her finger pinched between the ring members, particularly when the spring force from the housing is strong. Moreover, it is desirable that the unlocking and opening functions can be achieved with a single action or movement by a user so the ring mechanism is more convenient to use. It is also desirable to have a locking feature that automatically locks the ring binder when they are moved to the closed position so that a user may also close and lock the ring mechanism using a single action or movement.
Although using a control slide or travel bar having locking elements that block movement of hinge plates when in the locking position is an effective way to provide the desired locking features there are some costs associated with the control slide.